There is a liquid crystal lens device in which the distribution of the refractive index is changed according to an applied voltage by utilizing the birefringence of liquid crystal molecules. There is an image display device in which an image display unit is combined with the liquid crystal lens device. By changing the distribution of the refractive index of the liquid crystal optical element, the image display device switches between a state in which an image displayed by the image display unit is caused to be incident on the eyes of a viewer as displayed by the image display unit and a state in which the image displayed by the image display unit is caused to be incident on the eyes of the viewer as multiple parallax images. Thereby, a two-dimensional image display operation and a three-dimensional image display operation are realized. High display quality is desirable in such an image display device.